An example of a device to be used in specialized production or assembly machines is disclosed in Japanese Utility Model Kokoku-Kohou 60-17249. In this device, a fixed member pivotally supports the rotary shaft of a table that can freely rotate. This fixed member can easily supply drive fluid, electrical power, or signals to any device seated on the rotary table. For this purpose, a composite rotary joint is mounted on the aforesaid rotary shaft. This joint has the combined ability to carry fluids and connect electrical wiring. Through this composite rotary joint, the aforementioned working fluid and electricity can easily be supplied to operating actuators or control devices seated on the rotary table.
A brief explanation of a prior art device with reference to FIG. 3 is as follows. FIG. 3 shows a joint used in an automatic painting device with a multi-system paint circuit. This device requires three (3) systems including electrical wiring, a compressed air line, and a paint line for the spray gun.
In this prior art device, the main shaft 100 accommodates two separate pipes inside so that it is divided into two portions lengthwise. The air hose 116 is connected to an internal pipe 113 via rotary joint 112 on the lower end of portion 101 of the main shaft 100. On the other end of shaft portion 101 are the necessary number of air outlets 115, 115'.
The control circuit wiring 125 is run through the hollow outer portion 110 of bisected shaft 101 by way of current collector 119, which is fitted onto outer pipe 109 of rotary joint 112. An opposite end of the wire 125 extends through hole 108 located at the opposite end of shaft portion 101.
The wiring 125 is connected to solenoid valve 117 on circuit 121a, which is the circuit for various air distribution pipes furnished on rotary table 120. The air circuit 121a also connects through the exit tube 121b of the solenoid valve 117 to a spray gun (not pictured) on the rotary table 120.
A hose 126 for liquids is connected to central pipe 113 through rotary joint 114, which is located on the top end of a shaft portion 102 of the divided main shaft portion 100. The shaft portion 102 is located directly on top of the other shaft portion 101. On outer pipe 129 of the divided shaft is a casing 128 furnished with a ball bearing 127. The casing 128 is hermetically sealed by means of packing to seal rotary joint 130. The casing 128 on the rotary joint 130 has an inlet pipe 131 for accommodating paint, through which paint is supplied to air passage 107 in the main shaft.
The necessary number of exit holes 122 and 123 are provided for two separate paint systems in the divided main shaft 100. The paint pipes 124 connect these holes to the spray gun (not pictured) on rotary table 120. A drive motor 106 supplies rotary force to the main shaft 100 via sprockets 105.
In this prior art device, the wiring connection unit comprises a current collector (i.e. a rotary electrical joint) defined by rings surrounding the main shaft 100. As a result, the effective working area on the rotary table is diminished. The sprockets which supply rotation to both the table and the shaft, the current collector and the rotary joint to conduct pressurized air must all be arranged along the length of the shaft. In other words, the three aforementioned components must be arranged on the main shaft one atop the other, separated by tables serving to immobilize them. Inevitably, then, the device must have a high profile, and tends to be relatively large.
If the fixed table supporting the main shaft is positioned above the shaft, and the table which rotates with the shaft is positioned below the shaft, the arrangement of the pipes and wiring, installation and maintenance all become complicated, and the device becomes even larger.